There have been a variety of nozzles developed for use in fighting fires and for the production of foams for other purposes. Certain of such nozzles use only water as the extinguishing agent and are known as fog nozzles. Those 25 nozzles produce a dispersed spray of small water droplets projected from the nozzle tip in a generally conical pattern. An example of one such nozzle is described in U.S. Pat. No. 4,653,693.
A second type of nozzle commonly used in fire fighting is the air aspirating foam nozzle and a variety of such nozzles are described in the patent literature. Examples include U.S. Pat. No. 5,058,809 to Carroll et al.; U.S. Pat. No. 5,054,688 to Grindley; and U.S. Pat. No. 4,830,790 to Stevenson. The nozzles described in those exemplary patents all have in common means to aspirate air into a solution of foaming agent and water. Turbulence producing means provided within the nozzle body mix the air and liquid to produce a foam that is projected from the nozzle end.
A nozzle that might be considered a variation on those of the air aspirating type is disclosed in U.S. Pat. No. 5,113,945 to Cable. The Cable patent describes a foam producing nozzle that is supplied air from a pressurized source rather than aspirating atmospheric air for foam production as do the nozzles described in the patents cited above.
Yet other nozzles are of the multifunction type. Those are illustrated by a patent to Steingass, U.S. 4,944,460 and a second patent to Williams et al., U.S. Pat. No. 5,167,285. The nozzle described in the Steingass patent is adapted to spray either water or a mixture of water and a foam concentrate. It is adjustable between a straight stream and fog positions, and can be set to pull atmospheric air into the nozzle to mix with liquid and form a foam. The Williams et al. patent describes a nozzle that has provision for simultaneously discharging a dry powder and a stream of water or water based foam. The dry powder is discharged from a central, axially extending conduit while the liquid stream is discharged in an annular pattern around the stream of discharging powder. The powder, if it mixes at all with the liquid, does so after leaving the nozzle and at some distance therefrom.
Despite the variety of specialized nozzles and extinguishing agent delivery systems known in the prior art, the need for a simple high performance nozzle system capable of operating over a range of water pressures, and especially at low water pressures, to project an air aspirated stream of water or water-foam concentrate for considerable distances has not been met. Further, the art lacks a simple yet reliable system for continuously feeding particulate solids into a flowing liquid stream and thence through a nozzle without the hazard of bridging and clogging. Applicant's nozzle and accessory system meets those needs.